Batteries: more frequent, shallower cycling vs. less frequent, deeper cycling

[Dr Bob]

11 minutes ago, rusty69 said:

Has anyone mentioned Peukert yet? I feel he deserves a mention. What self respecting battery thread would be complete without the mention of Wilhelm Peukert and his law?

 

Apologies if he has already been mentioned, or is irrelevant to the discussion.

 

There. At least he has had a mention, relevant or not.

I dont bother with Peukert any more. I got Li's.

[rusty69]

3 minutes ago, Dr Bob said:

I dont bother with Peukert any more. I got Li's.

I've only got LA's. LA LA LA LA LA LA LA LA LA LA.

 

Bring back Gibbo!

 

 

[Dr Bob]

13 minutes ago, rusty69 said:

I've only got LA's. LA LA LA LA LA LA LA LA LA LA.

 

Bring back Gibbo!

 

 

Must be time for another stoooooory?

[rusty69]

Just now, Dr Bob said:

Must be time for another stoooooory?

Well......I notice Tumshie has a nano moth thread going, but not sure she is after the kinda stooooory we churned out last time.

[Dr Bob]

21 minutes ago, rusty69 said:

Well......I notice Tumshie has a nano moth thread going, but not sure she is after the kinda stooooory we churned out last time.

I hadn't noticed that one.

I'm off.

Whooooosh.

[dmr]

2 hours ago, Tony Brooks said:

 

No idea but they are almost certainly sulphated but still end up around 12.2 in the morning so acceptable (to me) capacity.

 

 

 There are several rested voltage to state of charge tables available and they seem to differ from make of battery to make. As far as I am concerned 12.2v to 12.3v is best considered as around 50% charged. I certainly do not believe 12.3V normally equates to 65% charged.

I used the Trojan figures to get 65% SoC. I use the Trojan specs because I feel they are believable and because I have Trojans . I would quite like to know why there are variations in these figures from different sources as all batteries use the same chemistry, or do things like the use of Antimony vs Calcium have an influence?  The other possible variable is the chosen strength of acid. It would be interesting to compare the SoC vs gravity figures from different manufacturers, I will put this on the big todo list.    Temperature is another variable, I think the Trojan figures are at quite a high temperature but I can't find this just now.

 

...............Dave

[Alan de Enfield]

4 hours ago, Mike the Boilerman said:

 

When I first started learning properly about batteries, I encountered the "never discharge below 50%" constantly but never saw "recharge to as close to 100% as soon as practicably possible". Few people ever say that until the person with the dead batteries says "but I NEVER discharged below 50%!", then out it comes. 

 

Until I read the Trojan data sheets that is, but even that's not quite what they say.

 

Trojan say words to the effect of "recharge immediately after discharge", IIRC. 

 

 

 

But, if you drank 1/2 of your glass of beer, and you went to the bar to re-fill it would you only take it to 75%, or 80%, or 'full to the brim'

 

I would take 're-charge' it to mean 'replace what you have used' and, as it was at 100% when you started to take it back to 100% SoC

 

Re-Charge = Refill = Replace

[cuthound]

12 minutes ago, dmr said:

I used the Trojan figures to get 65% SoC. I use the Trojan specs because I feel they are believable and because I have Trojans . I would quite like to know why there are variations in these figures from different sources as all batteries use the same chemistry, or do things like the use of Antimony vs Calcium have an influence?  The other possible variable is the chosen strength of acid. It would be interesting to compare the SoC vs gravity figures from different manufacturers, I will put this on the big todo list.    Temperature is another variable, I think the Trojan figures are at quite a high temperature but I can't find this just now.

 

...............Dave

 

Yes , alloying the plates with calcium decreases gassing and thus water consumption for a set voltage, reduces the need for equalization charges, lowers corrosion and reduces internal self discharge. Calcium is also cheaper than antimony and tin.

 

Alloying the plates with antimony and tin improves the batteries ability to be deeply discharged without damage, increases the number of discharge/charge cycles but increases water consumption. It also softens the plates, so plates nedd to vehicles for a given strength.

 

Hence leisure batteries tend to be of the lead calcium type and commercial/industrial batteries tend to use pure lead (VRSLA) or lead antimony alloyed plates (wet cells).

[dmr]

15 minutes ago, cuthound said:

 

Yes , alloying the plates with calcium decreases gassing and thus water consumption for a set voltage, reduces the need for equalization charges, lowers corrosion and reduces internal self discharge. Calcium is also cheaper than antimony and tin.

 

Alloying the plates with antimony and tin improves the batteries ability to be deeply discharged without damage, increases the number of discharge/charge cycles but increases water consumption. It also softens the plates, so plates nedd to vehicles for a given strength.

 

Hence leisure batteries tend to be of the lead calcium type and commercial/industrial batteries tend to use pure lead (VRSLA) or lead antimony alloyed plates (wet cells).

Yes, but does it have any influence on Specific Gravity vs Voltage vs State of Charge?

 

..............Dave

 

 

[dmr]

4 hours ago, Mike the Boilerman said:

 

When I first started learning properly about batteries, I encountered the "never discharge below 50%" constantly but never saw "recharge to as close to 100% as soon as practicably possible". Few people ever say that until the person with the dead batteries says "but I NEVER discharged below 50%!", then out it comes. 

 

Until I read the Trojan data sheets that is, but even that's not quite what they say.

 

Trojan say words to the effect of "recharge immediately after discharge", IIRC. 

 

 

There is a lot of conflicting information about, and if you waste an evening looking through all the Trojan documents on the www they actually conflict with themselves once or twice.

We know that batteries self discharge so surely this is the same as an intentional discharge and requires immediate action?, but in regard to stored batteries Trojan say:

 

"Monitor the specific gravity or voltage every 4-6 weeks. Stored batteries should be given a boost charge when they are at 70% state of charge (SOC) or less".

 

..............Dave

[MtB]

27 minutes ago, Alan de Enfield said:

I would take 're-charge' it to mean 'replace what you have used

 

Most relatively uninformed boaters don't the term 'recharge'. They say 'charge the batteries', by which they mean run the engine for an hour or two. 

 

When I charged my batteries, I meant I charged them until the Smartgauge said 100%. Which as any fule kno, is ridiculous way of expecting to know when the batteries are fully charged. 

 

 

[cuthound]

2 minutes ago, dmr said:

Yes, but does it have any influence on Specific Gravity vs Voltage vs State of Charge?

 

..............Dave

 

 

 

Yes, but only very slightly. Changing the make up of the plates changes to open circuit voltage of the battery.

 

This explains why different manufacturers show slightly different voltages for their SoC charts.

 

With specific gravity, the original strength of the acid needs to be taken into account. The strength varies according to the design use of the battery, and is a trade off between plate corrosion and performance.

[WotEver]

19 hours ago, cuthound said:

With specific gravity, the original strength of the acid needs to be taken into account. The strength varies according to the design use of the battery, and is a trade off between plate corrosion and performance

And I believe the strength also varies by region, with the tropics having a different strength to Europe, for example. Not that it’s relevant to this thread. 

[Wittenham]

this looks like the right thread in which to put this question:

 

If returning a bank of new batteries from 50% to 100% charge takes, say, four buckets of power:

• does it still take four buckets when the batteries are knackered?
• Or does it take less, because i get less usable power out before they are back to 50%?
• Or perhaps it takes more buckets of power because something is lost somewhere?  [in which case, per the rules of the man under the apple tree, where does the extra power go?]

This ties to the point made somewhere in this thread that the relative ability of a bank of batteries is not as important as enough power is coming out to do what i need to do.  But if degraded batteries are less efficient at converting those buckets of charging power into stuff i use, then it does become important [to me, anyway].

 

 

 

[Alan de Enfield]

28 minutes ago, Wittenham said:

this looks like the right thread in which to put this question:

 

If returning a bank of new batteries from 50% to 100% charge takes, say, four buckets of power:

• does it still take four buckets when the batteries are knackered?
• Or does it take less, because i get less usable power out before they are back to 50%?
• Or perhaps it takes more buckets of power because something is lost somewhere?  [in which case, per the rules of the man under the apple tree, where does the extra power go?]

This ties to the point made somewhere in this thread that the relative ability of a bank of batteries is not as important as enough power is coming out to do what i need to do.  But if degraded batteries are less efficient at converting those buckets of charging power into stuff i use, then it does become important [to me, anyway].

 

 

 

If a new battery has a capacity of 100Ah and you take it down to 50%, then you need to replace 50Ah to get back to 100%

If a 'knackered' battery now has a capacity of 50Ah due to sulphation and you take it down to 50% then you now need to replace only 25Ah to get it back to 100%

 

If 25Ah is sufficient for your usage then you didn't need a 100Ah battery in the 1st place, or, you didn't need discharge it to 50%

 

If you have a 10 litre bucket, whilst it is new it will contain 10 litres, empty it and it takes 10 litres to refill it.

If you use it for carrying cement about, after a while the old cement stuck to the sides will reduce the capacity to (say) 5 litres. You can now only get 5 litres of water out of it, but conversely it only takes 5 litres to fill it.

Edited October 31, 2019 by Alan de Enfield

[bizzard]

9 minutes ago, Wittenham said:

this looks like the right thread in which to put this question:

 

If returning a bank of new batteries from 50% to 100% charge takes, say, four buckets of power:

• does it still take four buckets when the batteries are knackered?
• Or does it take less, because i get less usable power out before they are back to 50%?
• Or perhaps it takes more buckets of power because something is lost somewhere?  [in which case, per the rules of the man under the apple tree, where does the extra power go?]

This ties to the point made somewhere in this thread that the relative ability of a bank of batteries is not as important as enough power is coming out to do what i need to do.  But if degraded batteries are less efficient at converting those buckets of charging power into stuff i use, then it does become important [to me, anyway].

 

 

 

Providing there's nothing faulty with the battery like dead cells but just old age sulfation and the capacity is falling,, yes its like having a gradually smaller and smaller capacity battery and with the same charger the charging time will get shorter and shorter as the newness continues to wear off until they're dead as a door nail.

[MtB]

25 minutes ago, Wittenham said:

If returning a bank of new batteries from 50% to 100% charge takes, say, four buckets of power:

 

"Power" incidentally, is the wrong way of thinking about it. Power takes into account time, and is the rate at which work is done, or the rate at which energy is expended. 

 

Your question would be better framed if you used the term 'energy' rather than power. Energy in this case is measured in Couloumbs, i.e. the energy expended (or charge transferred!) when a current of one Amp flows for one second. 

 

So yes, ignoring stuff like charge efficiency, the knackered battery would take half the energy, or half the number of Coulombs, to charge it as the new one.

 

 

 

 

 

 

 

Edited October 31, 2019 by Mike the Boilerman

[Wittenham]

that is clear, thanks all.

[Tony Brooks]

Towards the end of life the self discharge rate of batteries seems to increase and I put this down to small short circuits between plates probably caused by sediment build up. That means that even if we ignore sulphation you would have to put a little bit more in to get back to the same state of charge than you would with a new battery. Probably insignificant in the greater scheme of battery charging but still a factor.

[bizzard]

Bit like Nelsons Coulomb where the old sailors head is sulphated with pigeon poo.

 

 

[system 4-50]

On 31/10/2019 at 09:21, Alan de Enfield said:

If you have a 10 litre bucket, whilst it is new it will contain 10 litres, empty it and it takes 10 litres to refill it.

If you use it for carrying cement about, after a while the old cement stuck to the sides will reduce the capacity to (say) 5 litres. You can now only get 5 litres of water out of it, but conversely it only takes 5 litres to fill it.

but of course while it takes half the time to fill a bucket of half the capacity, batteries take signicantly more than half! (in case anybody new is looking in).